This application is related to and claims priority from Japanese Patent Applications No. 2000-255907 filed on Aug. 25, 2000 and No. 2001-121432 filed on Apr. 19, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an attachment structure of a door for adjusting an air flow. The present invention is suitably used for a vehicle air conditioner.
2. Description of Related Art
In a conventional door attachment structure for a vehicle air conditioner, a shaft is integrated with a flat door, and an end of the shaft is rotatably supported in an attachment hole of a case defining an air passage, so that the air passage is opened and closed by the flat door. Further, plural ribs (generally three), each of which has a triangle cross-section, are formed on an inner wall surface defining the attachment hole to protrude inside, and an outer surface of the door shaft is partially supported by the plural ribs. That is, for reducing the driving force of the door, a contact area between the outer surface of the door shaft and the inner wall surface defining the attachment hole is reduced.
However, for example, when the number of the ribs each having the triangle cross-section is three, the supporting area for supporting the outer surface of the door shaft is small. Therefore, the door shaft may tilt over when being into the attachment hole, and door attachment performance is deteriorated. On the other hand, if the number of the ribs is simply increased, a driving force for driving the door is increased.
In view of the foregoing problems, it is an object of the present invention to provide a door attachment structure which improves door attachment performance while door driving force is restricted from being increased.
According to the present invention, in a door attachment structure, a plurality of first ribs are provided on a part of an inner wall surface defining an attachment hole, in an axial direction of the attachment hole, to protrude to an outer surface of an insertion portion of the shaft inserted into the attachment hole; and a plurality of second ribs are provided on at least a part portion among the other part of the inner wall surface in the axial direction to protrude to the outer surface of the insertion portion of the shaft. In this attachment structure, the first ribs and the second ribs are positioned to be shifted from each other in a circumferential direction of the attachment hole. Therefore, the insertion portion of the shaft can be supported at points with the summation number of the first and second ribs. Furthermore, since the first and second ribs are shifted from each other in the axial direction, it can accurately prevent the shaft from being tilted in the attachment hole when the door is attached to the case. Therefore, the shaft can be smoothly inserted into the attachment hole, thereby improving attachment performance of the door.
Further, because the first ribs and the second ribs are formed to be separated from each other in the axial direction, each axial length of the first and second ribs is smaller than an entire axial length of the attachment hole. Therefore, when the door is operated, the contact area between the inner wall surface defining the attachment hole and the outer surface of the shaft can be restricted from being increased, and the driving force of the door can be reduced.